Add ability to detect GNU/Hurd when configuring.

Adapted from https://git.hadrons.org/cgit/debian/pkgs/pciutils.git/tree/debian/patches/00-configure-hurd.patch

From e39a3af22501234a91cf28e8c57b45f9379f9101 Mon Sep 17 00:00:00 2001
From: Damien Zammit <damien@zamaudio.com>
Date: Fri, 26 Oct 2018 09:24:04 -0400
Subject: [PATCH 2/2] Add ability to detect GNU/Hurd when configuring

---
 lib/configure |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/lib/configure
+++ b/lib/configure
@@ -25,7 +25,7 @@ if [ -z "$HOST" ] ; then
 		proc=`/usr/sbin/lsdev -C -c processor -S available -F name | head -1`
 		cpu=`/usr/sbin/lsattr -F value -l $proc -a type | sed 's/_.*//'`
 	else
-		cpu=`uname -m | sed 's/^i.86$/i386/;s/^sun4u$/sparc64/;s/^i86pc$/i386/;s/^BePC$/i386/;s/^BeMac$/powerpc/;s/^BeBox$/powerpc/'`
+		cpu=`uname -m | sed 's/^i.86-AT386/i386/;s/^i.86$/i386/;s/^sun4u$/sparc64/;s/^i86pc$/i386/;s/^BePC$/i386/;s/^BeMac$/powerpc/;s/^BeBox$/powerpc/'`
 	fi
 	if [ "$sys" = "DragonFly" ]
 	then
@@ -39,6 +39,10 @@ if [ -z "$HOST" ] ; then
 	then
 		sys=cygwin
 	fi
+	if [ "$sys" = "GNU" ]
+	then
+		sys=gnu
+	fi
 	HOST=${3:-$cpu-$sys}
 fi
 [ -n "$RELEASE" ] && rel="${RELEASE}"
